Urea backflow prevention apparatus of scr and a control method thereof

ABSTRACT

A urea backflow prevention apparatus of Selective Catalytic Reduction (SCR) system that injects a urea aqueous solution to an exhaust pipe may include a urea tank storing the urea aqueous solution, a nozzle being installed on the exhaust pipe and injecting the urea aqueous solution into the exhaust pipe, a supply pump pressurizing the urea aqueous solution in order to inject the urea aqueous solution from the nozzle to the exhaust pipe, a suction line supplying the urea aqueous solution stored in the urea tank to the supply pump by connecting the urea tank and the supply pump, a pressure line delivering the urea aqueous solution pressurized at the supply pump to the nozzle by connecting the supply pump and the nozzle, and a return line collecting urea aqueous solution not injected at the nozzle to the urea tank by connecting the supply pump and the urea tank.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2014-0155997, filed Nov. 11, 2014, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a urea backflow prevention apparatus of SCR and a control method thereof, and more particularly, to a urea backflow prevention apparatus of SCR and a control method thereof that prevents a breakage of a supply pump due to the freezing of urea aqueous solution flowed backward.

2. Description of Related Art

There have been the problems of serious environmental pollution by emissions exhausted from internal combustion engines of vehicles using fossil fuel such as gasoline or diesel. In particular, the discharging of soot, nitrogen oxides (NOx) and fine dust including soot exhausted from diesel vehicles such as buses and trucks are perceived as a serious problem, and thus, each country controls strictly emission of exhaust gas by preparing related regulations in order to solve exhaust gas problems of such above diesel vehicles.

Generally, the exhaust system of a diesel engine is provided with an exhaust gas post-processing device such as Diesel Oxidation Catalyst (DOC), Diesel Particulate matter Filter (DPF), Selective Catalyst Reduction (SCR) and Lean NOx Trap (LNT) and so on in order to reduce the pollutants contained in the exhaust gas such as carbon monoxide (CO), hydrocarbon (HC), particulate matter, and nitrogen oxides (NOx), and so on.

Among them, an exhaust gas post-processing device (hereinafter, referred to as “SCR system”) using an SCR may function as injecting a reducing agent such as urea inside an exhaust pipe and thereby reducing nitrogen oxides in the exhaust gas to nitrogen and oxygen. In other words, the above SCR system injects a reducing agent such as urea into an exhaust pipe, and then the reducing agent is converted to ammonia (NH3) by the heat of exhaust gas, thereby reducing nitrogen oxides (NOx) to nitrogen gas (N2) and water (H2O) by a catalytic reaction of nitrogen oxides (NOx) and ammonia in the exhaust gas via the SCR catalyst.

FIG. 1A and FIG. 1B are views illustrating the SCR system according to the related art and FIG. 2A and FIG. 2B are views illustrating problems of the SCR system according to the related art.

Referring to FIG. 1A, FIG. 1B, FIG. 2A and FIG. 2B, the SCR system in accordance with the related art pressurizes the urea aqueous solution stored in a urea tank via a pump in order to inject it through a nozzle into the exhaust pipe during normal operation (refer to FIG. 1A). In addition, when an engine is stopped, the SCR system collects again the urea aqueous solution to the urea tank (refer to FIG. 1B). The purpose of collecting the urea aqueous solution is to prevent breakage of parts of the SCR system due to the increasing of the urea volume by freezing when the temperature is lowered in the winter.

However, if a vehicle mounted with the SCR system based on a conventional technology is parked outside for a long time in the winter after the urea aqueous solution has been all collected, the temperature inside the SCR system will drop from a normal operation temperature (about 40□) to below zero as the temperature inside the SCR system goes in equilibrium with outdoor temperature. In this case, the pressure in an internal flow path in the closed SCR system which was in equilibrium with the atmospheric pressure when collecting the urea aqueous solution may be lowered (refer to FIG. 2A) and thereby the urea aqueous solution inside a urea tank may flow backward to a supply pump through a suction line (refer to FIG. 2B). Therefore, a problem occurred that a supply pump was broken if the urea aqueous solution flowed backward was frozen.

The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing a urea backflow prevention apparatus of SCR and a control method thereof which prevents a urea aqueous solution in a urea tank inside of a stopped vehicle from being flowed backward to a supply pump through a suction line.

According to various aspects of the present invention, a urea backflow prevention apparatus of Selective Catalytic Reduction (SCR) system that injects a urea aqueous solution to an exhaust pipe may include a urea tank storing the urea aqueous solution, a nozzle being installed on the exhaust pipe and injecting the urea aqueous solution into the exhaust pipe, a supply pump pressurizing the urea aqueous solution in order to inject the urea aqueous solution from the nozzle to the exhaust pipe, a suction line supplying the urea aqueous solution stored in the urea tank to the supply pump by connecting the urea tank and the supply pump, a pressure line delivering the urea aqueous solution pressurized at the supply pump to the nozzle by connecting the supply pump and the nozzle, and a return line collecting urea aqueous solution not injected at the nozzle to the urea tank by connecting the supply pump and the urea tank.

The urea backflow prevention apparatus of SCR may further include a shut-off valve disposed on the suction line and opening and closing the suction line.

The urea backflow prevention apparatus of SCR may further include a urea detection device being provided in any one or more of the supply pump or the pressure line, and detecting whether the urea aqueous solution exists in any one or more of the supply pump or the pressure line after the operation of the SCR system is terminated.

The urea backflow prevention apparatus of SCR may further include a control unit that receives a signal of whether the urea aqueous solution exists in any one or more of the supply pump or the pressure line from the urea detection device and transmits a signal for the shut-off valve to open and close the suction line after the operation of the SCR system is terminated.

The urea tank may include a ventilating opening opened to atmosphere.

The return line may be formed to be shorter than the suction line so that a lower part of the return line may be continuously positioned on the surface of the urea aqueous solution inside of the urea tank.

According to various aspects of the present invention, a control method for a urea backflow prevention apparatus of Selective Catalytic Reduction (SCR) may include an engine stop determination step by a control unit of determining whether an engine of a vehicle is stopped, a urea collection step of collecting a urea aqueous solution inside of a pressure line, a supply pump and a suction line by operating the supply pump in the reverse direction, when it is determined that the engine is stopped at the engine stop determination step, a urea collection completion determination step of determining whether the collection of the urea aqueous solution has been completed by the control unit receiving a signal on whether the urea aqueous solution exists in any one or more of the supply pump or the pressure line from a urea detection device, after the urea collection step, and a shut-off valve closure step of closing a shut-off valve by transmitting a signal from the control unit to the shut-off valve, when it is determined by the control unit that the collection of the urea aqueous solution has been completed, after the urea collection completion determination step.

The control method for the urea backflow prevention apparatus of SCR may further include an engine operation determination step of determining whether the engine is operated again by the control unit, after the shut-off valve closure step.

The control method for the urea backflow prevention apparatus of SCR may, further include a shut-off valve open step of opening the shut-off valve by transmitting a signal from the control unit to the shut-off valve, when it is determined by the control unit that the engine is operated again at the engine operation determination step.

As described above, according to the present invention, breakage of a supply pump by freezing of a urea aqueous solution flowed backward may be prevented.

It is understood that the term “vehicle” or “vehicular” or other similar terms as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g., fuel derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example, both gasoline-powered and electric-powered vehicles.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B are views illustrating a SCR system according to the related art.

FIG. 2A and FIG. 2B are views illustrating a problem of the SCR system according to the related art.

FIG. 3 is a view illustrating an exemplary urea backflow prevention apparatus of SCR according to the present invention.

FIG. 4A and FIG. 4B are views illustrating an operation of the exemplary urea backflow prevention apparatus of SCR according to the present invention.

FIG. 5 is a flow chart of an exemplary control method of a urea backflow prevention apparatus of SCR according to the present invention.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

FIG. 3 is a view illustrating a urea backflow prevention apparatus of SCR according to various embodiments of the present invention. Referring to FIG. 3, the urea backflow prevention apparatus of SCR according to various embodiments of the present invention may include a urea tank 10, a nozzle 20, a supply pump 30, a suction line 40, a pressure line 50, a return line 60, a shut-off valve 70, a urea detection device 80 and control unit 90.

The urea tank 10 may store a urea aqueous solution. The urea tank 10 may include a ventilating opening 11. The ventilating opening 11 may perform a role of discharging the inside air of the urea tank 10. Moreover, as described later, the operation of the SCR system is terminated and after the collecting the urea aqueous solution is completed, the internal pressure of the SCR system may be maintained as atmospheric pressure and equilibrium by the ventilating opening 11.

The nozzle 20 may be installed on the exhaust pipe and perform a role of injecting the urea aqueous solution to the exhausted pipe.

The supply pump 30 may perform a role of pressuring the urea aqueous solution so that the urea aqueous solution is injected from the nozzle 20 to the exhaust pipe. Furthermore, as described later, the supply pump 30 may operate for collecting the urea aqueous solution in the reverse direction after the operation of the SCR system is terminated such that it may perform a role of collecting the urea aqueous solution inside of the system of SCR to the urea tank 10.

The suction line 40 may connect the supply pump 30 and the urea tank 10. Thus, the suction line 40 may perform a role of supplying the urea aqueous solution stored in the urea tank 10 to the supply pump 30. To this end, a lower part of the suction line 40 is preferably positioned below the surface of the urea aqueous solution stored in the urea tank 10.

The pressure line 50 may connect the nozzle 20 and the supply pump 30. Thus, the pressure line 50 may perform a role of delivering the urea aqueous solution pressurized at the supply pump 30 to the nozzle 20.

The return line 60 may connect the urea tank 10 and the supply pump 30. Thus, the return line 60 may perform a role of collecting the urea aqueous solution not injected from the nozzle 20. The return line 60 may be formed to be shorter than the suction line 40 so that the lower part of the return line 60 is always preferably positioned on the surface of the urea aqueous solution inside of the urea tank 10.

The shut-off valve 70 may be disposed on the suction line 40. Accordingly, the shut-off valve 70 may perform a role of opening and closing the suction line 40. The shut-off valve 70 may close the suction line 40 after the operation of the SCR (Selective Catalytic Reduction) system is terminated so that it may prevent a breakage of the supply pump 30 when the urea aqueous solution inside of the urea tank 10 flows backward to the supply pump 30 through the suction line 40 (refer to FIG. 2B) and the urea aqueous solution flowed backward is frozen.

The urea detection device 80 may be provided on any one or more of the supply pump 30 or the pressure line 50. The urea detection device 80 detects whether the urea aqueous solution exists in any one or more of the supply pump 30 or the pressure line 50 after the operation of the SCR (Selective Catalytic Reduction) system is terminated. Accordingly, the urea detection device 80 may perform a role of detecting whether all urea aqueous solution is collected to the urea tank 10 after the operation of the SCR (Selective Catalytic Reduction) system is terminated.

The control unit 90 may receive a signal of whether the urea aqueous solution exists in any one or more of the supply pump 30 or the pressure line 50 from the urea detection device 80 after the operation of the SCR (Selective Catalytic Reduction) system is terminated. Also, the control unit 90 may transmit a signal in order that the shut-off valve 70 opens and closes the suction line 40.

FIG. 4A and FIG. 4B are views illustrating an operation of the urea backflow prevention apparatus of SCR according to various embodiments of the present invention. Referring FIG. 4A, during normal operation of the SCR system, the shut-off valve 70 is opened and the supply pump 30 is operated in the forward direction. Thus, the urea aqueous solution stored in the urea tank 10 is moved to the supply pump 30 along the suction line 40 and the urea aqueous solution pressurized at the urea supply pump 30 is supplied to the nozzle 20 along the pressure line 50 and injected into the exhaust pipe. At this time, the urea aqueous solution which might not be injected into the exhaust pipe is again collected to the urea tank 10 along return line 60.

Also, when the urea aqueous solution is collected, the shut-off valve 70 is opened and the supply pump 30 is operated in the reverse direction. Accordingly, the urea aqueous solution remaining in the pressure line 50, the supply pump 30 or the suction line 40 is again collected to the urea tank 10.

Referring to FIG. 4B, after the operation of the SCR system and the collecting of the urea aqueous solution have been completed, the shut-off valve 70 is closed. Accordingly, since the suction line 40 is closed, the urea aqueous solution does not flow backward unlike the related art even though the temperature of the SCR system falls down.

FIG. 5 is a flow chart of a control method of the urea backflow prevention apparatus of SCR according to various embodiments of the present invention. Referring to FIG. 5, a control method for the urea backflow prevention apparatus of SCR in accordance with another embodiment of the present invention may include an engine stop determination step S100, a urea collection step S200, a urea collection completion determination step S300, a shut-off valve closure step S400, the engine operation determination step S500 and the shut-off valve open step S600.

The engine stop determination step S100 is a step of determining whether an engine of a vehicle is stopped. After the engine is stopped, the urea aqueous solution is collected only when the exhaust gas is not discharged.

The urea collection step S200 is a step of collecting the urea aqueous solution inside of the pressure line 50, the supply pump 30 and the suction line 40 by operating the supply pump 30 in the reverse direction, when it is determined that the engine is stopped at the engine stop determination step S100. The purpose of collecting the urea aqueous solution is to prevent breakage of parts of the SCR system because the volume of the urea is increased due to freezing on the spot when the temperature is lowered in the winter.

The urea collection completion determination step S300 is a step of determining whether the collection of the urea aqueous solution has been completed by the control unit 90 receiving the signal on whether the urea aqueous solution exists in any one or more of the supply pump 30 or the pressure line 50 from the urea detection device 80, after the urea collection step S200.

The shut-off valve closure step S400 is a step of closing the shut-off valve 70 by transmitting the signal from the control unit 90 to the shut-off valve 70, when it is determined that the collection of the urea aqueous solution has been completed, after the urea collection completion determination step S300. Accordingly, since the suction line 40 is closed, the urea aqueous solution does not flow backward unlike the related art even though the temperature of the SCR system drops.

The engine operation determination step S500 is a step of determining whether the engine operates again at the control unit 90, after the shut-off valve closure step S400. Also, the shut-off valve open step S600 is a step of opening the shut-off valve 70 by transmitting the signal from the control unit 90 to the shut-off valve 70, when the control unit 90 determines that the engine is operated again at the engine operation determination step S500. When the engine is restarted, since the urea aqueous solution in the exhaust pipe is again injected in order to purify NOx in the exhaust gas, it is determined whether the engine restarts. In addition, when the engine is restarted, the shut-off valve 70 is re-opened in order to inject the urea aqueous solution in the exhaust pipe and the urea aqueous solution stored in the urea tank 10 is supplied to the supply pump 30.

For convenience in explanation and accurate definition in the appended claims, the terms “upper” or “lower”, “inner” or “outer” and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. 

What is claimed is:
 1. A urea backflow prevention apparatus of Selective Catalytic Reduction (SCR) system that injects a urea aqueous solution to an exhaust pipe, the urea backflow prevention apparatus of SCR comprising: a urea tank storing the urea aqueous solution; a nozzle being installed on the exhaust pipe and injecting the urea aqueous solution into the exhaust pipe; a supply pump pressurizing the urea aqueous solution of the urea tank to inject the urea aqueous solution from the nozzle to the exhaust pipe; a suction line supplying the urea aqueous solution stored in the urea tank to the supply pump by connecting the urea tank and the supply pump; a pressure line connecting the supply pump and the nozzle and delivering the urea aqueous solution pressurized at the supply pump to the nozzle; and a return line collecting a urea aqueous solution not injected at the nozzle to the urea tank by connecting the supply pump and the urea tank.
 2. The urea backflow prevention apparatus of the SCR system of claim 1, further comprising a shut-off valve disposed on the suction line and selectively opening the suction line.
 3. The urea backflow prevention apparatus of the SCR system of claim 2, further comprising a urea detection device being provided in at least one of the supply pump and the pressure line, and detecting whether the urea aqueous solution exists in the at least one of the supply pump and the pressure line after an operation of the SCR system is terminated.
 4. The urea backflow prevention apparatus of the SCR system of claim 3, further comprising a controller receiving a signal of whether the urea aqueous solution exists in the at least one of the supply pump and the pressure line from the urea detection device and transmits a signal for the shut-off valve to selectively open the suction line after the operation of the SCR system is terminated.
 5. The urea backflow prevention apparatus of the SCR system of claim 1, wherein the urea tank comprises a ventilating opening opened to atmosphere.
 6. The urea backflow prevention apparatus of the SCR system of claim 2, wherein the return line is formed to be shorter than the suction line so that a lower part of the return line is continuously positioned on a surface of the urea aqueous solution inside of the urea tank.
 7. A control method for a urea backflow prevention apparatus of Selective Catalytic Reduction (SCR), comprising: an engine stop determination step by a controller of determining whether an engine of a vehicle is stopped; a urea collection step of collecting a urea aqueous solution inside of a pressure line, a supply pump and a suction line by operating the supply pump in a reverse direction, when the engine is determined to be stopped at the engine stop determination step; a urea collection completion determination step of determining whether the collection of the urea aqueous solution has been completed by the controller receiving a signal on whether the urea aqueous solution exists in at least one of the supply pump and the pressure line from a urea detection device, after the urea collection step; and a shut-off valve closure step of closing a shut-off valve by transmitting a signal from the controller to the shut-off valve, when it is determined by the controller that the collection of the urea aqueous solution has been completed, after the urea collection completion determination step.
 8. The control method for the urea backflow prevention apparatus of the SCR of claim 7, further comprising an engine operation determination step of determining whether the engine is operated again by the controller, after the shut-off valve closure step.
 9. The control method for the urea backflow prevention apparatus of the SCR of claim 8, further comprising a shut-off valve open step of opening the shut-off valve by transmitting a signal from the controller to the shut-off valve, when it is determined by the controller that the engine is operated again at the engine operation determination step. 